1. Field of the Invention
The present invention relates to a wheel bearing device for supporting wheels, for example, for an automobile.
2. Description of the Related Art
Wheel bearing devices are generally classified into those for drive-wheel applications and driven-wheel applications. The wheel bearing device for drive wheels, for example, includes a wheel hub and a double-row bearing. Some devices are further attached with a constant velocity joint and formed into a unit.
One of the bearing devices for drive wheels has a construction in which one of the double-row inner races of the bearing is formed on an outer periphery of the wheel hub and the other is formed on an outer periphery of an outer joint member of the constant velocity joint. In the bearing device of this kind, the wheel hub and the constant velocity joint must be coupled together to achieve relative positioning of the double-row inner races and to maintain certain pre-load applied to the inside of the bearing. According to some recently proposed method, a method of coupling them by swaging as shown, e.g., in Japanese Patent Laid-Open Publication No. 2001-18605, which is considered advantageous in terms of effective use of axial space of the bearing and improvement of the rigidity of the coupled portion. With this method, a stem portion of the outer joint member is plastically deformed in a direction in which the diameter is expanded radially outward so that it firmly engages with irregular portions formed in the inner periphery of the wheel hub.
Recently, in the field of wheel bearing devices, there is not only a strong demand for more lightweight compact devices, but also quality and reliability improvement and cost reduction have been in urgent demand.
The present invention is directed to a solution to the demand, and it is a first object of the invention to provide a wheel bearing device that allows high workability and high joining strength to be achieved in such a swaging process at low cost.
It is a second object of the invention to provide a wheel bearing device whose coupling portion is kept from loosening by a large moment load acting upon it and to increase resistance against pull out (pull-out resistance) with a simple structure.